1. Field of the Invention
The present invention relates to a process for guidance, containment, treatment and imaging of contaminants and other substances in a subsurface environment, utilizing ferrofluids.
Ferrofluids are stable colloidal suspensions of ferromagnetic particles in carrier liquids. The solid, single-domain magnetite particles have an average diameter of 10 nm and are covered with a molecular layer of dispersant. Brownian motion keeps the particles suspended, while the dispersant coating prevents the particles from agglomerating. The stability of ferrofluids means that neither external magnetic fields nor gravity can significantly change the concentration of the magnetic particles in the carrier liquid. Consequently, ferrofluids move as a homogeneous pseudo-single-phase fluid when flowing under the influence of a magnetic field. This attribute is responsible for the unique property of ferrofluids enabling them to be manipulated through the application of external magnetic fields in virtually any fashion defying gravitational or viscous forces. Therefore, ferrofluids can be made to flow in a desired direction and move precisely without any physical contact. Additionally, ferrofluids cast a strong magnetic signature through their distinct magnetic and electrical resistance properties.
2. The Relevant Art
Due to their ability to be held in place by magnetic fields, ferrofluids currently find application in a variety of products, including (a) hermetic seal pumps, where ferrofluids are used to eliminate leakage along rotating shafts and joints, (b) rotating vacuum seals used in semiconductor processing and environmentally controlled chambers, and (c) high-fidelity audio speakers and precision bearings. The biomedical field has exploited ferrofluids for use in (a) tracing blood flow in non-invasive circulatory measurements, and (b) transporting therapeutic agents incorporated onto the magnetic particles, which are then guided by magnetic fields to specific body sites. A detailed treatment of ferrofluid physics can be found in Rosensweig (1985), while more applied aspects are discussed in Raj and Moskowitz (1990), Berkovski et al. (1993), and Berkovski and Bashtovoy (1996), references listed in the Relevant Art section infra.